1. Field of the Invention
The present invention relates to received signal strength indicators (hereinafter, also referred to as an “RSSI”) detecting the power of an RF signal and the like, and more particularly, to received signal strength indicators self-calibrating a gain of a limiter to maintain a constant gain over internal and external variations, such as temperature and process variations.
2. Description of the Related Art
In general, a received signal strength indicator (RSSI) is used to detect the power of an RF signal that is received from a receiver. The RSSI includes a multi-stage amplifier and a plurality of rectifiers. The multi-stage amplifier includes a plurality of limiters connected in series to each other to amplify the received signal in multiple stages. The plurality of rectifiers rectify individual outputs of the limiters included in the multi-stage amplifier, and generate a voltage having a magnitude corresponding to the strength of the received signal. The RSSI may be used for gain calibration of the entire RF system by using a feedback structure.
The RSSI may be manufactured as an RF IC by using a semiconductor process. Because of characteristics of an analog circuit implemented as the RF IC, the characteristics can be changed due to temperature or process variations. For example, variations may occur in the gain of the limiter included in the RSSI, and variations may occur in a direct current output of the rectifier.
Therefore, in the RSSI-related technical field, there has been required a method of calibrating a gain of a limiter and a direct current output of a rectifier according to temperature or process deviations.